Question

The two types of first-class STL containers are sequence containers and __________ containers.

Short answer

The two types of first-class STL containers are sequence containers and associative containers.

Step-by-step solution

Understanding the question

Identify the type of the second category of first-class STL containers.

Recalling STL container categories

Remember that the Standard Template Library (STL) in C++ has several categories of containers. Two of the main categories are sequence containers and the other type we need to identify.

Identifying the second type of container

The second type of first-class STL container is associative containers.

Key concepts

Sequence Containers

In the world of C++, sequence containers are a fundamental part of the Standard Template Library (STL). These containers maintain the order of insertion for the elements they hold, which means that elements are placed sequentially according to the order in which they're added.

Popular sequence containers include

• std::vector
• std::deque
• std::list
• std::forward_list
• std::array

Each container has its specific use case, for example, std::vector is highly efficient for accessing elements by index and good for adding elements at the end, while std::list is optimal for inserting elements at any position. Knowing when to use which sequence container is key for writing efficient C++ programs.

Associative Containers

Opposite to sequence containers, associative containers in C++ STL store elements following a specific ordering based on the element's key, or in an unordered fashion that uses hash codes for organizing elements. Unlike sequence containers, they provide faster element search, insertion, and deletion operations, independent of the container's size.

The associative containers include

• std::set
• std::multiset
• std::map
• std::multimap

And the unordered varieties

• std::unordered_set
• std::unordered_multiset
• std::unordered_map
• std::unordered_multimap

For example, std::map is a sorted associative array that is accessed by keys, whereas std::unordered_map uses hashing to allow for constant time complexity on average for addition, searching, and deletion operations.

Standard Template Library

The Standard Template Library, commonly known as STL, is a powerful collection of C++ template classes that provide general-purpose classes and functions with templates and algorithms. The beauty of STL is in its ability to allow programmers to create efficient programs by providing a foundation of linked structures, arrays, and algorithms.

STL is divided into four main components:

• Containers
• Algorithms
• Iterators
• Functors

Containers, such as sequence and associative containers, hold data. Algorithms perform operations on the data, iterators provide a way to access each element held in a container, and functors are function objects that can be used in conjunction with STL algorithms. Embracing STL enables code reusability and high abstraction while sustaining performance.

C++

C++ is a general-purpose programming language that has been around since the early 1980s. It is an extension of the C programming language, with added features such as object-oriented programming, templates, and exceptions which allow for more complex and abstract software development.

C++ is used in various domains, from system/software development to game development, and it is celebrated for its speed and efficiency. Understanding C++ and its features like the STL is crucial for anyone looking to create high-performance applications. Moreover, with the continuous updates to the language, learning C++ is an ongoing process, as new features like lambda expressions, auto keyword, and smart pointers keep enhancing the language's capabilities.